MIL-STD-2197A(SH)
5.5.1 Seawater static sealing surfaces. The application for seawater static sealing surfaces shall be as follows:
a. Type of damage: corrosion pits, scratches, gouges, and mismachining
b. Typical work-pieces: flanges, valve and pump mating surfaces, all types of static sealing surfaces including, but not limited to, 0-ring grooves and submarine main shaft seal static sealing surfaces
c. Typical base metals: nickel-copper, copper-nickel, bronzes, stainless steels, or chrome plated steel
d. Allowed build-up thicknesses: not greater than 0.030 inch over wide surfaces, no limit on thickness filling pits, provided pits do not compromise pressure boundary strength (Thickness limitations imposed by the qualified procedure shall be observed.)
e. Soft metals: Tin, indium, and copper
f. Top coat: Not required (If a nickel top coat is applied, an alkaline or neutral pH solution shall be used when plating over tin filler (to prevent dissolution of the tin) and an acidic pH solution shall be used when plating nickel or nickel-tungsten over copper.)
g. Authorization: all applications authorized
5.5.2 Steam static sealing surfaces. The application for steam sealing surfaces shall be as follows:
a. Type of damage: scratches, corrosion, steam cuts, and mismachining b. Typical work-pieces: flanges and valve turbine mating surfaces
c. Typical base: carbon steel, alloy steel, and chromium stainless metals steel
d. Allowed build-up thickness: not greater than 0.050 inch over wide surface (No limit on filling pits, provided that pits do not compromise pressure boundary strength. Thickness limitation imposed by the qualified procedure shall be observed.)
e. Typical filler metals: silver, copper
f. Typical top coat metals: none required
g. Authorization: all applications authorized
5.5.3 Machinery static mating surfaces. The procedure for machinery static mating surfaces shall be as follows:
a. Type of damage: fretting, mismachining, misalignment, and corrosion
b. Typical work-pieces: motor or generator bell housings, motor or generator shafts at rolling element bearing fit area, keyways, and cylinder heads
c. Typical base metals: steels, bronze, copper-nickel, and nickel-copper d. Allowed build-up thickness: not greater than 0.030 inch
e. Not greater than 0.030 inch: nickel, copper, and silver
f. Typical top coat: none required (When damage is caused by fretting, 0.0003 to 0.0005 inch of tin or tin- indium may be applied over the hard top coat to prevent further fretting.)
g. Authorization: all applications authorized
5.5.4 Printed circuit repairs. Printed circuit repairs are authorized using approved procedures.
5.6 Class 3 (sliding contact surface) coatings. Allowable thicknesses shall be limited to not more than 0.025 inch exclusive of filling pits, scores, and other imperfections, when the total surface area of the defects comprises not more than 10 percent of the area to be plated. The maximum allowable plating thickness shall not exceed the qualification limit of the procedure. Class 3 brush plated surfaces are generally for wear resistance. Shaft journals,
hydraulic cylinders, pistons, rams, valve stems, electrical contacts, and commutators are examples of equipment that is plated for wear resistance. The following is a typical application of this class:
a. Type of damage: wear, scoring, corrosion, or mismachining
b. Typical work-pieces: straight shafts and crankshafts and valve stems in packing area c. Typical base: steels, stainless steels, bronze, metals nickel copper, and chromium
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